#include <functional>

#include <cstdio>


using Handler = std::function<void(int)>;

Handler getHandler()
{
    return Handler();
}

int main()
{
    printf("handler:%d\n", bool(getHandler()));

    Handler h = [](int i) {return i;};
    printf("handler:%d\n", bool(h));

    return 0;
}
